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Related Articles:  Plants/Planting for PondsLandscape Plants, Waterlilies, Snails: Bane or Boon, Livestocking a PondPond Maintenance, Spring Pond Maintenance, Winter Maintenance Pond Algae Control,

/Aquatic Gardens, Design, Construction & Maintenance

Pond Plant Care

By Bob Fenner

 Keep them in control or else!

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

V. 1 Print and eBook on Amazon
V. 2 Print and eBook on Amazon 

by Robert (Bob) Fenner

We have already covered the "how" and "when" of caring for aquatic plants in previous articles; here we'll continue with aspects of ongoing up-keep. There are at least two main ways of approaching this material; by topic (e.g. fertilization, pest control) and chronological application. Let's do the former here and offer a time-line checklist under the heading: Maintenance; General Care For Your Pond.

Physical Maintenance:

Starting in early to later Spring, depending on how cold a climate you live in, some routine (weekly) removal of unwanted "trash" and "rotting" plant material is instigated. You want to balance such "house-keeping" efforts with the aesthetic advantages to be gained against the wear and tear that you'll be causing your plant stocks; especially if they're all just been re-planted or installed for the first time (due to it being a new system or freshly "defrosted").

As with roses, fruit trees et alia, there is no general consensus as to how to go about this. A few of my own perspectives and techniques: For lilies, lotus and their family (Nymphaeaceae) relatives, whose petioles and pads age/die as they are turning from yellow to brown, are best pinched off by crushing near their base. Large, emergent, spade like leaves of plants as irises may be handily cut at an angle near the waters surface. Take care not to pull on rooted plants as this will likely stir up the soil at their base, stirring nutrient release and algal growth.

Thinning out floating plants by removing larger, older material is a good idea; crowded individuals display less flowering and stringy, non-energetic growth.

Folks with small ponds, with much plant matter and cold winters should especially cut back, remove excess growth in advance of very cold water. By clipping back emergent and floating plants, as well as lilies, the effects of decomposition will be lessened.


Aquatic plants have all the same nutrient (and other growing) requirements as terrestrials. Fortunately most chemical needs are met with ambient water-soluble materials and fish wastes. Some growers and hobbyists find it expedient to "boost" growth and blooming with "complete" (N, P, K) or partial fertilizers, with or without other adjuncts.

In general, I am opposed to promoting the use of organic sources of nutrients (manures, "meals") in favor of inorganics. Further, I am leery the continuous, monthly feedings endorsed and promoted by other writers. It is my opinion that such "boosting" is unnecessary and frequently harmful. Please hear me out.

I suggest that you utilize a time-release format inorganic "tablet" or granular source for limiting nutrients that can be applied during annual re-planting or other occasion when you need to "get into" the pond. More frequent ventures damage plants and too often result in the plant food being released into the water, spurring algal growth and dangerously altering water chemistry.

There is one piece of "killer technology" that I would like to share with you that is used extensively in the commercial culture of plants (and fishes) and by "professional" pond service people that is not widespread in hobbyist circles; and it really works. This is the careful use of limestone, a form of calcium carbonate (CaCO3) blended in with the pot or planting bed soil. There are so many benefits to limestone use that we'll devote adequate coverage here to explain them all and urge your use.

First of all, a few precautions, powdered limestone is safe and effective when used properly, but it can be a hazard to you and your pond if mis-applied. This dry, white, water-loving molecule is caustically alkaline; of a basic (high) pH. Therefore you want to keep your exposure (eyes, skin, breathing) to a minimum. Wear gloves and work in a non-breezy environment. The same goes for the use in the pond; you want the limestone mixed in the soil, not resting on top or mixed freely in your water. Is this clear?

The calcium in limestone is an essential component to plant growth and hence a useful fertilizer, but it does much more:

1) Limestone helps balance/buffer the loss of alkaline reserve in your ponds soil and water, preventing precipitous drops in pH. The processes in a "closed" pond (one where new water is not continuously running in and overflowing out), tends to be "reductive", going acidic over time with plant growth and fish feeding. Your water may have substantial buffering capacity, and proper filtration and water changes help, but the use of limestone is one further help/margin of safety.

2) The addition of calcium aids other processes in the pond, like the hardening of snail and crustacean shells.

3) The addition of limestone can aid in sterilizing the soil, and keep down microbial population explosions.

4) Liming adds to the decomposition of bottom sediments and biological ooze.

5) Mixing in limestone helps to neutralize the harmful effects of organic and inorganic acids.

6) Lime helps to clean and clear your water by helping to flocculate clay in muddy water.

7) Lime helps to "free-up" other nutrients to your plants, particularly phosphorus. This is a very important phenomenon. You could have all the phosphorus bound up next to your plants; at too low a pH none would be available for their use.

How much limestone do you want to add? About a teaspoon per gallon of soil. Dice, blend it in when re/potting, and fertilizing your plants. Where can you get this "wonder" additive? At your nearby garden center. This and other sources of lime are used for similar purposes in terrestrial applications.

A final note for those interested in liming for all the good it can do them; there are formulas for determining how much more limestone is of benefit to add on the basis of mud (soil) and system water pH. For folks with very acidic soil and/or water with a total hardness or alkalinity of less than 10 parts per million, you may very well want to consider using a test kit and adding more lime. To all, take your time, and remember, it's better to add less lime than too much.

Don't forget your potted pond plants need to be on a schedule for replacement of fertilizers and other amendments. I put a note on my annual calendar for replacement/augmentation dates. Here are some potted Clover and Iris. 

Pest Control:

The serious infectious, parasitic and predatory pests of aquatic plants are thankfully few. The few real "plagues" are best and easily avoided rather than "cured"; by buying or collecting clean specimens, inspecting and quarantining new introductions or relying on a reputable dealer to do the same for you.

Dips/Baths: There are some notable fungus diseases of water lilies, the ever-present possibility of snails et al. unwanted hitchhikers, that may be further eliminated by the use of preventative dips. There are commercial preparations for these or you may elect to "make your own". The most common prophylactic baths incorporate either the strong oxidant, potassium permanganate (KMnO3), or the innocuous flocculent alum (aluminum sulfate). Concentrations and instructions for their use are enclosed with their packaging, but basically a solution is prepared and the new plant material emersed for several minutes. The plants are subsequently rinsed and placed.

If you do nothing else with new arrivals, do look them over carefully, trim off dead/dying material, scrape away snail and insect eggs and hose off vigorously before putting them in your pond.

Bug-gy Pests: that "come in" from outside are another matter. Aphids can be a real bane especially on water lilies where they'll cause so much destruction from their piercing and sucking that pads will dwindle and flowering come to a standstill. Watch for the appearance of winged females in the Spring when they descend from certain species of nearby trees. If you act quickly, small populations of their offspring may be washed off by a strong blast of tap water or my favorite, the arrangement of sprinklers to "shoot" over and onto the pond plants when you're watering the surrounding landscape. Disagreeable numbers of aphids may be handily destroyed by spraying a dilute solution of Volck (tm) oil onto them. This material is safe for use in ponds with other life unlike pesticides and other "economic poisons".

There are numerous "flies" (e.g. caddis, midge species) and beetles that prey on aquatic plants. For the most part they should be treated by simply removing the offended parts of the plants. Be careful in enlisting helpful advice. Many folks suggest the use of organophosphate "bug-sprays", nicotine (yes, the same toxin in cigarettes, cigars, chaw), and other poisons. Please don't get involved in using these in or around your water; they're toxic to you and your other livestock, and many are biologically and physically persistent. A biological agent, the bacteria Bacillus thuringiensis is sometimes efficacious and is safe to use rather than chemical controls.

About snails; most are pests and to be avoided as carriers of disease for livestock and humans. If you intend to utilize their services, make sure and intentionally procure single-sex species, like the mystery, apple snails in the genus Pomacea (formerly Ampullaria), or the desirable Ramshorn snail (Planorbis corneus). Please see a following piece for more on these mollusks. Should your pond become infested or over-populated with snails, a lettuce leaf "trap" floated on the surface for a day aids in their collection for destruction.

Aquatic Gardens

Ponds, Streams, Waterfalls & Fountains:
Volume 1. Design & Construction
Volume 2. Maintenance, Stocking, Examples

V. 1 Print and eBook on Amazon
V. 2 Print and eBook on Amazon 

by Robert (Bob) Fenner
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